Method of producing a fuel additive

ABSTRACT

A method of producing a fuel additive includes passing a feed stream comprising C4 hydrocarbons through a butadiene extraction unit producing a first process stream; passing the first process stream through a methyl tertiary butyl ether unit producing a second process stream and a methyl tertiary butyl ether product; passing the second process stream through a hydration unit producing the fuel additive and a recycle stream; passing the recycle stream through a hydrogenation unit; and recycling the recycle stream to a steam cracker unit and/or to the feed stream

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application of PCT/US2019/026985,filed Apr. 11, 2019, which is incorporated herein by reference in itsentirety, and which claims the benefit of U.S. Provisional ApplicationNo. 62/660,200, filed Apr. 19, 2018.

BACKGROUND

Commercial gasoline, which is fuel for internal combustion engines, is arefined petroleum product that is typically a mixture of hydrocarbons(base gasoline), additives, and blending agents. Additives and blendingagents are added to the base gasoline to enhance the performance and thestability of gasoline, for example octane boosters.

When used in high compression internal combustion engines, gasoline hasthe tendency to “knock.” Knocking occurs when combustion of the air/fuelmixture in the cylinder does not start off correctly in response toignition because one or more pockets of air/fuel mixture pre-igniteoutside the envelope of the normal combustion front. Anti-knockingagents, also known as octane boosters, reduce the engine knockingphenomenon, and increase the octane rating of the gasoline

Hydrocarbon cracking processes are important conversion processes usedin petroleum refineries. For example, fluid catalytic cracking (FCC) iswidely used to convert the high-boiling, high-molecular weighthydrocarbon fractions of petroleum crude oils to more valuable gasoline,olefinic gases, and other products. Thermal cracking of naphtha and gasoil is also widely used in the petrochemical industry to produce avariety of olefins and aromatics. For example, hydrocarbon feed stockscan be mixed with steam and subjected to elevated temperatures (e.g.,700-900° C.) in a steam cracker furnace wherein the feed stockcomponents are cracked into various fractions. The effluent of the steamcracker can contain a gaseous mixture of hydrocarbons, for example,saturated and unsaturated olefins and aromatics (C1-C35). The effluentcan then be separated into individual olefins (for example, ethylene,propylene, and C4's) and pyrolysis gasoline. Recycle streams of crudehydrocarbons are often formed as by-products during these crackingprocesses.

The presence of isobutylene, butadiene, 1-butene, 2-butene, and othercomponents within the crude hydrocarbon streams can allow for theformation of valuable alcohols and fuel additives. However, theconversion of crude hydrocarbon streams to fuel additive products canoften be inefficient and costly. Furthermore, the final productspecifications for such alcohols can be undesirable and can fail to meetmarket quality requirements. For example, alcohol products can have highlevels of impurities, high Reid vapor pressures, e.g., greater than 2.0pounds per square inch (psi) (greater than 10 kilopascals, greater than12 kilopascals, greater than 13 kilopascals, greater than 14kilopascals), and low octane numbers (e.g., 82 Research Octane Number(RON)), all of which correlate with poor product quality. Anyimprovement in these specifications and/or the efficiency of the processcan provide a more valuable fuel additive product.

Thus, there is a need for an efficient method of producing fueladditives that can make use of crude hydrocarbon streams and producefinal products with lower impurities and higher performancespecifications.

SUMMARY

Disclosed, in various embodiments, are methods of producing fueladditives.

A method of producing a fuel additive comprises: passing a feed streamcomprising C4 hydrocarbons through a butadiene extraction unit producinga first process stream; passing the first process stream through amethyl tertiary butyl ether unit producing a second process stream and amethyl tertiary butyl ether product; passing the second process streamthrough a hydration unit producing the fuel additive and a recyclestream; passing the recycle stream through a hydrogenation unit; andrecycling the recycle stream to a steam cracker unit and/or to the feedstream.

A method of producing a fuel additive, comprising: passing a feed streamcomprising C4 hydrocarbons through a catalytic cracking unit; passingthe feed stream through a butadiene extraction unit producing a firstprocess stream, wherein the butadiene extraction unit comprisesextractive distillation, solvent degassing, solvent regeneration,solvent recovery, or a combination thereof; withdrawing a butadieneproduct from the butadiene extraction unit; passing the first processstream through a methyl tertiary butyl ether unit producing a secondprocess stream and a methyl tertiary butyl ether product; withdrawingthe methyl tertiary butyl ether product from the methyl tertiary butylether unit; passing the second process stream through a hydration unitproducing the fuel additive and a recycle stream, wherein a temperaturewithin the hydration unit is 30° C. to 250° C., a pressure within thehydration unit is 500 kiloPascals to 20,000 kiloPascals, and whereingreater than or equal to 1.0% by weight of any butenes present in thesecond process stream is converted to butanol within the hydration unit;withdrawing the fuel additive from the hydration unit, wherein the fueladditive comprises 2-butanol, tert-butyl alcohol, di-isobutene, or acombination thereof; passing the recycle stream through a hydrogenationunit, wherein greater than or equal to 0.001% by weight of any butenepresent in the recycle stream is converted to butane within thehydrogenation unit; and recycling the recycle stream to the catalyticcracking unit.

These and other features and characteristics are more particularlydescribed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings wherein likeelements are numbered alike and which are presented for the purposes ofillustrating the exemplary embodiments disclosed herein and not for thepurposes of limiting the same.

The FIGURE is a schematic diagram representing a unit sequence forproducing fuel additives.

DETAILED DESCRIPTION

Disclosed herein is an efficient method of producing fuel additives thatcan make use of crude hydrocarbon streams and produce final productswith low impurities and high performance specifications. For example,the method disclosed herein can provide a unique sequence of unitoperations that converts crude hydrocarbons into valuable alcohol fueladditives. This unique sequence can significantly improve the efficiencyof the process, thereby reducing total capital costs. The final fueladditive products can have levels of 2-butanol, tert-butyl alcohol,C4-dimer, or a combination thereof, for example, the final fuel additiveproducts can have levels of the C4-dimer comprising trimethylpentane,di-isobutylene, 2,2,4 trimethylpentane, 2,3,3 trimethylpentane, or acombination thereof in an amount of 0.01 weight % to 50 weight %, basedon the total weight of the fuel additive, high octane numbers (e.g.,greater than or equal to 85 RON, or greater than or equal to 87 RON),and low Reid vapor pressures of greater than or equal to 55 Kilopascals.For example, the trimethylpentane can be present in an amount of 0.1 to25 weight percent, for example, 1 to 20 weight %. Any one or all ofthese properties can correlate with high performance and high marketvalue. The method disclosed herein can also produce secondary productsalong with the fuel additive product. For example, methyl tertiary butylether (MTBE) products can be produced along with the fuel additive, thusmaximizing the efficiency and productivity of the process.

The method can include passing a feed stream of crude hydrocarbonsthrough a butadiene extraction unit producing a first process stream.This butadiene extraction unit can remove the butadiene present in thefeed stream. The minimization of butadiene in the process increasesdesirable product specifications. The first process stream can then bepassed through a MTBE unit. The MTBE unit can convert isobutylenepresent in the first process stream to a MTBE product and a secondprocess stream. The second process stream can then be passed through ahydration unit to produce a fuel additive, for example, an alcohol fueladditive. A recycle stream can also be produced in the hydration unit.The recycle stream can be recycled through an additional hydrogenationunit and returned to a point in the process before the MTBE unit. Forexample, the recycle stream can be recycled to a steam cracker unitand/or to the feed stream. The present process can maximize productquality for a fuel additive product while also producing additional MTBEproducts in an efficient manner.

The method disclosed herein can include passing a feed stream through anolefin production unit, for example, a hydrocarbon cracking unit, forexample, a catalytic and/or steam cracking unit, such that a source ofthe feed stream can include a product of an olefin cracking processand/or an olefin production process. The feed stream can comprisehydrocarbons, for example, C4 hydrocarbons. Additional hydrocarbons, forexample, C2 and C3 hydrocarbons, can also be fed to the olefinproduction unit. The feed stream can be withdrawn from the olefinproduction unit as a crude C4 hydrocarbon stream. The stream produced bythe olefin production unit can comprise propane, propylene, ethylacetylene, vinyl acetylene, 1,3-butadiene, 1,2-butadiene, isobutylene,cis-2-butene, trans-2-butene, 1-butene, isobutane, n-butane, or acombination thereof. The total C4 olefin content of the feed stream whenwithdrawn from a steam cracking unit can be greater than or equal to 90%by weight and the feed stream can comprise greater than or equal to 40%by weight isobutylene. The total C4 olefin content of the feed streamwhen withdrawn from a fluid catalytic cracking unit can be greater thanor equal to 50% by weight and the feed stream can comprise greater thanor equal to 30% by weight isobutane.

The feed stream can be passed through a butadiene extraction unit. Thebutadiene extraction unit can be an optional component that can be usedin addition to the extraction unit if excess butadiene slippage occurs.The butadiene extraction unit can comprise a butadiene extractivedistillation column and other components in series. For example, thebutadiene extraction unit can comprise a butadiene extractivedistillation column, followed by solvent degassing, solventregeneration, and solvent recovery. The butadiene unit can be operatedat a temperature of less than or equal to 150° (300° F.) and a pressureof 700 kilopascals (100 pounds per square in gauge). A liquid solventselected from a single compound or a mixture of aromatic or aliphaticsolvents, preferably toluene, benzene, ethylbenzene, cumene, xylenes,mesitylene, hexane, octane, cyclohexane, olefins, preferably, hexene,heptane, octane, or ethers, preferably diethylether, tetrahydrofurane,dimethylformamide, n-methyl-pyrrolidone, acetonitrile, furfural,N-methyl-2-pyrrolidone, acetone, dimethylacetamide, cuprous ammoniumacetate or β-methoxypropionitrile, more preferably an aromatic solvent,most preferably n-methyl-pyrrolidone can be used. This butadieneextraction unit can remove butadiene present in the process stream.Accordingly, a first product stream, i.e., a butadiene product stream,can be withdrawn from the butadiene extraction unit. The butadieneproduct can be withdrawn with a purity of greater than or equal to 90%.The first process stream, now with reduced butadiene content, can bewithdrawn from the butadiene extraction unit and transferred to anotherunit. The process stream being withdrawn from the butadiene extractionunit can comprise less than or equal to 5% butadiene by weight, forexample, less than or equal to 3%, for example, less than or equal to1%.

The first process stream can then be passed through a hydrogenationunit, for example, a selective hydrogenation unit. For example, thehydrogenation unit can be a selective butadiene hydrogenation unit. Thehydrogenation unit can convert butadiene present in the first processstream to 1-butene, cis-2-butene, and trans-2-butene. The conversionrate from butadiene to 1-butene, cis-2-butene, and trans-2-butene can begreater than or equal to 90%. Propylene, ethyl acetylene, and vinylacetylene present in the first process stream can also undergohydrogenation within the hydrogenation unit. The selective hydrogenationcatalyst can comprise palladium with an aluminum base. The hydrogenationcatalyst can comprise platinum, rhodium, palladium, ruthenium, cobalt,nickel, copper, or a combination thereof. Hydrogen can be injected intothe first process stream prior to passing through the reactor.

The first process stream exiting the hydrogenation unit can then bepassed through a MTBE unit. Methanol can be fed through the MTBE unitvia a methanol stream. The MTBE unit can convert isobutylene present inthe first process stream to a MTBE product. The first process stream canbe contacted with the methanol and a catalyst, for example, an acidicion-exchange resin catalyst, within the MTBE unit. Methanol andisobutylene can be present within the MTBE unit in a molar ratio of 1.0mole of isobutylene to 0.05 moles to 10.0 moles of methanol, forexample, one mole of isobutylene to 0.1 moles to 5.0 moles of methanol,for example, one mole of isobutylene to 0.5 moles to 2.0 moles ofmethanol. The MTBE product can be withdrawn from the MTBE unit via aMTBE product stream. The purity of the MTBE product can be greater thanor equal to 95%. The conversion rate from isobutylene to MTBE within theMTBE unit can be greater than or equal to 75%, for example, greater thanor equal to 85%, for example, greater than or equal to 95%. The secondprocess stream can then be withdrawn from the MTBE unit with reducedisobutylene content. For example, the second process stream exiting theMTBE unit can comprise less than or equal to 5% isobutylene. Atemperature within the MTBE unit can be 15° C. to 150° C., for example,35° C. to 125° C. A pressure within the MTBE unit can be 500 kiloPascalsto 2800 kiloPascals, for example, 1000 kiloPascals to 2000 kiloPascals,for example, 1500 kiloPascals. The MTBE unit can also produce a secondprocess stream.

The second process stream exiting the MTBE unit can then be passedthrough a hydration unit to produce a fuel additive, for example, analcohol fuel additive. The second process stream entering the hydrationunit can comprise less than or equal to 5% butadiene by weight, forexample, less than or equal to 3%, for example, less than or equal to1%. The fuel additive product can be withdrawn from the hydration unitvia a product stream. Water can be fed to the hydration unit via a waterstream. The hydration unit can comprise an oscillating baffle reactor, afixed bed reactor, a membrane integrated reactor, or a combinationthereof. The hydration unit can convert butene present in the processstream to butanol. For example, greater than or equal to 90% of thebutene present in the feed stream can be converted to butanol within thehydration unit. The second process stream can be contacted with waterand a catalyst within the hydration unit. For example, the catalyst cancomprise phosphoric acid, hypophosphorous acid, an ion-exchange resin,sulfur, polystyrene, polymer, niobium oxide, or a combination thereof.Water and butene can be present within the hydration unit in a molarratio of 1.0 mole of water to 1 mole to 20 moles of butene, for example,one mole of water to 5 moles to 10 moles of butene. A temperature withinthe hydration unit can be 30° C. to 250° C., for example, 100° C. to200° C. A pressure within the hydration unit can be 500 kiloPascals to20,000 kiloPascals, for example, 5000 kiloPascals to 10,000 kiloPascals,for example, 7500 kiloPascals.

The fuel additive product can comprise 2-butanol, tert-butyl alcohol,C4-dimer, or a combination thereof, for example, the C4-dimer cancomprise di-isobutylene, 2,2,4 trimethylpentane, 2,3,3 trimethylpentane,or a combination thereof. The fuel additive product can comprise greaterthan or equal to 0.1% by weight trimethylpentane, for example, greaterthan or equal to 0.5% by weight, for example, greater than or equal to1.0% by weight. An octane number of the fuel additive product can begreater than or equal to 80 for example, greater than or equal to 82,for example, greater than or equal to 85, for example, greater than orequal to 87, for example, greater than or equal to 90 according to theAnti-Knock Index, for example, greater than or equal to 85, for example,90.

The octane number is a standard measurement used to gage the performanceof an engine or fuel. The higher the octane number, the more compressionthe fuel is able to withstand before igniting. Fuels with higher octaneratings are generally used in high performance gasoline engines thatneed higher compression ratios. Fuels with lower octane numbers can bedesirable for diesel engines because diesel engines do not compress thefuel, but rather compress only air and then inject fuel into the airwhich is heated by compression. Gasoline engines rely on ignition of airand fuel compressed together as a mixture, which is ignited at the endof the compression stroke using spark plugs. As a result, highcompressibility of fuel is a consideration for gasoline engines.

The Anti-Knock Index is measured by adding the research octane numberand the motor octane number and dividing by two, i.e., (RON+MON)/2. TheResearch Octane Number is determined by running the fuel in a testengine at a speed of 600 revolutions per minute with a variablecompression ratio under controlled conditions, and comparing the resultswith those for mixtures of iso-octane and n-heptane. Motor Octane Numberis determined by testing a similar test engine to that used indetermining the Research Octane Number but at a speed of 900 revolutionsper minute with a preheated fuel mixture, higher engine speed, andvariable ignition timing. Depending on the composition, the Motor OctaneNumber can be about 8 to 12 octanes lower than the Research OctaneNumber. The research octane number can be greater than or equal to 80,for example, greater than or equal to 85, for example, greater than orequal to 90. The motor octane number can be greater than or equal to 70,for example, greater than or equal to 75, for example, greater than orequal to 80, for example, greater than or equal to 82. Higher octaneratings can give higher amounts of energy needed to initiate combustion.Fuels with higher octane ratings are less prone to auto-ignition and canwithstand a greater rise in temperature during the compression stroke ofan internal combustion engine without auto-igniting.

Reid vapor pressure is used to measure the volatility of gasolinedefined as the absolute vapor pressure exerted by a liquid at 37.8° C.as determined by ASTM D-323. The measures the vapor pressure of gasolinevolatile crude oil, and other volatile petroleum products, except forliquefied petroleum gases. Reid vapor pressure is measured inkiloPascals and represents a relative pressure to atmospheric pressuresince ASTM D-323 measures the gage pressure of the sample in anon-evacuated chamber. High levels of vaporization are desired forwinter starting and operation and lower levels are desirable in avoidingvapor lock during summer heat. Fuel cannot be pumped when vapor ispresent in the fuel line and winter starting will be difficult whenliquid gasoline in the combustion chambers has not vaporized. This meansthat the Reid vapor pressure is changed accordingly by oil producersseasonally to maintain gasoline engine reliability. The Reid vaporpressure of the fuel additive product can be less than or equal to 25kiloPascals, for example, less than or equal to 15 kiloPascals, forexample, less than or equal to 10 kiloPascals. The fuel additive productcan also comprise less than or equal to 10% impurities formed bydimerization of C4 olefins such as isobutylene, 1-butene, 2-butene orcombinations thereof.

A recycle stream, e.g., a hydrocarbon recycle stream, can be withdrawnfrom the hydration unit and recycled to a steam cracker unit and/or theinitial feed stream. The recycle stream can comprise 1-butene, 2-butene,isobutane, n-butane, or a combination thereof. The recycle stream canoptionally be passed through a drying unit for trace water removal and arecycle hydrogenation unit prior to returning to the initial feedstream. The recycle hydrogenation unit can convert the 1-butene and2-butene present in the recycle stream to n-butane and isobutane. Forexample, greater than or equal to 90% of any butene present in thehydrocarbon recycle stream can be converted to butane within thehydrogenation unit.

A more complete understanding of the components, processes, andapparatuses disclosed herein can be obtained by reference to theaccompanying drawings. These figures (also referred to herein as “FIG.”)are merely schematic representations based on convenience and the easeof demonstrating the present disclosure, and are, therefore, notintended to indicate relative size and dimensions of the devices orcomponents thereof and/or to define or limit the scope of the exemplaryembodiments. Although specific terms are used in the followingdescription for the sake of clarity, these terms are intended to referonly to the particular structure of the embodiments selected forillustration in the drawings, and are not intended to define or limitthe scope of the disclosure. In the drawings and the followingdescription below, it is to be understood that like numeric designationsrefer to components of like function.

Referring now to the FIGURE, this simplified schematic diagramrepresents a unit sequence 10 used in a method for producing fueladditives. The sequence 10 can include passing a feed stream comprisinghydrocarbons through a hydrocarbon cracking unit 14. For example, thehydrocarbon cracking unit 14 can be a steam cracking and/or a catalyticcracking unit.

A first process stream 16 can then be withdrawn from the cracking unit14 and sent to a butadiene extraction unit 18. The first process stream16 can comprise crude hydrocarbons, for example, C4 hydrocarbons. Thebutadiene extraction unit 18 can comprise a butadiene extractivedistillation column and other components in series. This butadieneextraction unit 18 can remove butadiene present in the first processstream 16. Accordingly, a butadiene product stream 19 can be withdrawnfrom the butadiene extraction unit 18.

A second process stream, now with reduced butadiene content, can bewithdrawn from the butadiene extraction unit 18. The second processstream 24 can then be passed through an MTBE unit 26. Methanol can befed through the MTBE unit 26 via stream 20. The MTBE unit 26 can convertisobutylene present in the second process stream 24 to an MTBE product.This MTBE product 22 can be withdrawn from the MTBE unit 24. A thirdprocess stream 28 can then be withdrawn from the MTBE unit 26, nowcomprising a reduced isobutylene content.

The third process stream 28 can then be passed through a hydration unit30 to produce a fuel additive product 46, for example, an alcohol fueladditive. The fuel additive product 46 can be withdrawn from thehydration unit 30. Water can be fed to the hydration unit 30 via stream44.

A recycle stream 32, for example, a hydrocarbon recycle stream, can bewithdrawn from the hydration unit 30 and recycled to the initial feedstream 12. The recycle stream 32 can be passed through a recyclehydrogenation unit 42 prior to returning to the feed stream 12. Theresulting hydrogenated recycle stream 48 can then be combined with thefeed stream 12.

The methods disclosed herein include(s) at least the following aspects:

Aspect 1: A method of producing a fuel additive, comprising: passing afeed stream comprising C4 hydrocarbons through a butadiene extractionunit producing a first process stream; passing the first process streamthrough a methyl tertiary butyl ether unit producing a second processstream and a methyl tertiary butyl ether product; passing the secondprocess stream through a hydration unit producing the fuel additive anda recycle stream; passing the recycle stream through a hydrogenationunit; and recycling the recycle stream to a steam cracker unit and/or tothe feed stream.

Aspect 2: The method of Aspect 1, wherein a source of the feed streamcomprises a product of an olefin cracking process and/or an olefinproduction process.

Aspect 3: The method of any of the preceding aspects, wherein the feedstream comprises propane, propylene, ethyl acetylene, vinyl acetylene,1,3-butadiene, 1,2-butadiene, isobutylene, cis-2-butene, trans-2-butene,1-butene, isobutane, n-butane, or a combination thereof.

Aspect 4: The method of any of the preceding aspects, wherein thebutadiene extraction unit comprises extractive distillation, solventdegassing, solvent regeneration and/or solvent recovery.

Aspect 5: The method of any of the preceding aspects, wherein less thanor equal to 50% by weight of any butadiene present in the feed stream isextracted by the butadiene extraction unit, preferably wherein 20 to 50%by weight of any butadiene present in the feed stream is extracted bythe butadiene extraction unit.

Aspect 6: The method of any of the preceding aspects, further comprisingcontacting the first process stream with a catalyst within the methyltertiary butyl ether unit, wherein the catalyst comprises an acid-typeion-exchange resin.

Aspect 7: The method of any of the preceding aspects, wherein atemperature within the methyl tertiary butyl ether unit is 15° C. to150° C. and a pressure within the methyl tertiary butyl ether unit is500 kiloPascals to 2800 kiloPascals.

Aspect 8: The method of any of the preceding aspects, wherein methanoland isobutylene are present in the methyl tertiary butyl ether unit in amolar ratio of one mole of isobutylene to 0.05 moles to 10 moles ofmethanol, preferably wherein the molar ratio is 0.1 to 5.

Aspect 9: The method of any of the preceding aspects, wherein greaterthan or equal to 1.0% by weight of any isobutylene present in the firstprocess stream is converted to methyl tertiary butyl ether within themethyl tertiary butyl ether unit, preferably wherein 5 to 35% by weightis converted.

Aspect 10: The method of Aspect 9, further comprising withdrawing amethyl tertiary butyl ether product from the methyl tertiary butyl etherunit.

Aspect 11: The method of any of the preceding aspects, wherein thesecond process stream comprises less than or equal to 3.0% butadiene byweight prior to passing through the hydration unit.

Aspect 12: The method of any of the preceding aspects, furthercomprising contacting the second process stream with a catalyst withinthe hydration unit, wherein the catalyst comprises phosphoric acid,hypophosphorous acid, ion-exchange resin, sulfur, polystyrene, polymer,niobium oxide, or a combination thereof.

Aspect 13: The method of any of the preceding aspects, wherein atemperature within the hydration unit is 30° C. to 250° C. and apressure within the hydration unit is 500 kiloPascals to 20,000kiloPascals.

Aspect 14: The method of any of the preceding aspects, wherein greaterthan or equal to 1.0% by weight of any butene present in the secondprocess stream is converted to butanol within the hydration unit,preferably wherein 1 to 50% by weight is converted.

Aspect 15: The method of any of the preceding aspects, furthercomprising withdrawing a fuel additive product from the hydration unit.

Aspect 16: The method of Aspect 15, wherein the fuel additive productcomprises 2-butanol, tert-butyl alcohol, di-isobutene, or a combinationthereof.

Aspect 17: The method of Aspect 15 or Aspect 16, wherein an octanenumber of the fuel additive product is greater than 85 in accordancewith the Anti-Knock Index.

Aspect 18: The method of any of Aspects 15-17, wherein a Reid vaporpressure of the fuel additive product is less than or equal to 15kiloPascals.

Aspect 19: The method of any of the preceding aspects, wherein greaterthan or equal to 0.001% by weight of any butene present in the recyclestream is converted to butane within the hydrogenation unit, preferablywherein 0.001 to 2% by weight is converted.

Aspect 20: A method of producing a fuel additive, comprising: passing afeed stream comprising C4 hydrocarbons through a catalytic crackingunit; passing the feed stream through a butadiene extraction unitproducing a first process stream, wherein the butadiene extraction unitcomprises extractive distillation, solvent degassing, solventregeneration, solvent recovery, or a combination thereof; withdrawing abutadiene product from the butadiene extraction unit; passing the firstprocess stream through a methyl tertiary butyl ether unit producing asecond process stream and a methyl tertiary butyl ether product;withdrawing the methyl tertiary butyl ether product from the methyltertiary butyl ether unit; passing the second process stream through ahydration unit producing the fuel additive and a recycle stream, whereina temperature within the hydration unit is 30° C. to 250° C., a pressurewithin the hydration unit is 500 kiloPascals to 20,000 kiloPascals, andwherein greater than or equal to 1.0% by weight of any butenes presentin the second process stream is converted to butanol within thehydration unit; withdrawing the fuel additive from the hydration unit,wherein the fuel additive comprises 2-butanol, tert-butyl alcohol,di-isobutene, or a combination thereof; passing the recycle streamthrough a hydrogenation unit, wherein greater than or equal to 0.001% byweight of any butene present in the recycle stream is converted tobutane within the hydrogenation unit; and recycling the recycle streamto the catalytic cracking unit.

In general, the invention may alternately comprise, consist of, orconsist essentially of, any appropriate components herein disclosed. Theinvention may additionally, or alternatively, be formulated so as to bedevoid, or substantially free, of any components, materials,ingredients, adjuvants or species used in the prior art compositions orthat are otherwise not necessary to the achievement of the functionand/or objectives of the present invention. The endpoints of all rangesdirected to the same component or property are inclusive andindependently combinable (e.g., ranges of “less than or equal to 25 wt%, or 5 wt % to 20 wt %,” is inclusive of the endpoints and allintermediate values of the ranges of “5 wt % to 25 wt %,” etc.).Disclosure of a narrower range or more specific group in addition to abroader range is not a disclaimer of the broader range or larger group.“Combination” is inclusive of blends, mixtures, alloys, reactionproducts, and the like. Furthermore, the terms “first,” “second,” andthe like, herein do not denote any order, quantity, or importance, butrather are used to denote one element from another. The terms “a” and“an” and “the” herein do not denote a limitation of quantity, and are tobe construed to cover both the singular and the plural, unless otherwiseindicated herein or clearly contradicted by context. “Or” means“and/or.” The suffix “(s)” as used herein is intended to include boththe singular and the plural of the term that it modifies, therebyincluding one or more of that term (e.g., the film(s) includes one ormore films). Reference throughout the specification to “one embodiment”,“another embodiment”, “an embodiment”, and so forth, means that aparticular element (e.g., feature, structure, and/or characteristic)described in connection with the embodiment is included in at least oneembodiment described herein, and may or may not be present in otherembodiments. In addition, it is to be understood that the describedelements may be combined in any suitable manner in the variousembodiments.

The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (e.g.,includes the degree of error associated with measurement of theparticular quantity). The notation “±10%” means that the indicatedmeasurement can be from an amount that is minus 10% to an amount that isplus 10% of the stated value. The terms “front”, “back”, “bottom”,and/or “top” are used herein, unless otherwise noted, merely forconvenience of description, and are not limited to any one position orspatial orientation. “Optional” or “optionally” means that thesubsequently described event or circumstance can or cannot occur, andthat the description includes instances where the event occurs andinstances where it does not. Unless defined otherwise, technical andscientific terms used herein have the same meaning as is commonlyunderstood by one of skill in the art to which this invention belongs. A“combination” is inclusive of blends, mixtures, alloys, reactionproducts, and the like. In a list of alternatively useable species, “acombination thereof” means that the combination can include acombination of at least one element of the list with one or more likeelements not named. Also, “at least one of” means that the list isinclusive of each element individually, as well as combinations of twoor more elements of the list, and combinations of at least one elementof the list with like elements not named.

All cited patents, patent applications, and other references areincorporated herein by reference in their entirety. However, if a termin the present application contradicts or conflicts with a term in theincorporated reference, the term from the present application takesprecedence over the conflicting term from the incorporated reference

While particular embodiments have been described, alternatives,modifications, variations, improvements, and substantial equivalentsthat are or may be presently unforeseen may arise to applicants orothers skilled in the art. Accordingly, the appended claims as filed andas they may be amended are intended to embrace all such alternatives,modifications variations, improvements, and substantial equivalents.

What is claimed is:
 1. A method of producing a fuel additive,comprising: passing a feed stream comprising C4 hydrocarbons through abutadiene extraction unit producing a first process stream; passing thefirst process stream through a methyl tertiary butyl ether unitproducing a second process stream and a methyl tertiary butyl etherproduct; passing the second process stream through a hydration unitproducing the fuel additive and a recycle stream, wherein the secondprocess stream comprises butene, and wherein at least a portion of thebutene present in the second process stream is converted to butanolwithin the hydration unit; passing the recycle stream through a recyclehydrogenation unit; and recycling the hydrogenated recycle stream fromthe recycle hydrogenation unit to a steam cracker unit and/or to thefeed stream.
 2. The method of claim 1, wherein a source of the feedstream comprises a product of an olefin cracking process and/or anolefin production process.
 3. The method of claim 1, wherein the feedstream comprises at least one of propane, propylene, ethyl acetylene,vinyl acetylene, 1,3-butadiene, 1,2-butadiene, isobutylene,cis-2-butene, trans-2-butene, 1-butene, isobutane, or n-butane.
 4. Themethod of claim 1, wherein the butadiene extraction unit comprisesextractive distillation, solvent degassing, solvent regeneration and/orsolvent recovery.
 5. The method of claim 1, wherein the feed streamcomprises butadiene, and wherein the first process stream withdrawn fromthe butadiene extraction unit comprises less than or equal to 5%butadiene by weight.
 6. The method of claim 1, further comprisingcontacting the first process stream with a catalyst within the methyltertiary butyl ether unit, wherein the catalyst comprises an acid-typeion-exchange resin; and wherein the second process stream exiting themethyl tertiary butyl ether unit comprises less than or equal to 5%isobutylene by weight.
 7. The method of claim 1, wherein a temperaturewithin the methyl tertiary butyl ether unit is 15° C. to 150° C. and apressure within the methyl tertiary butyl ether unit is 500 kiloPascalsto 2800 kiloPascals.
 8. The method of claim 1, wherein methanol andisobutylene are present in the methyl tertiary butyl ether unit in amolar ratio of one mole of isobutylene to 0.05 moles to 10 moles ofmethanol.
 9. The method of claim 1, wherein the first process streamcomprises isobutylene, and wherein greater than or equal to 75% byweight of the isobutylene present in the first process stream isconverted to methyl tertiary butyl ether within the methyl tertiarybutyl ether unit.
 10. The method of claim 1, further comprisingwithdrawing the methyl tertiary butyl ether product from the methyltertiary butyl ether unit; wherein the purity of the methyl tertiarybutyl ether product is greater than or equal to 95%.
 11. The method ofclaim 1, wherein the second process stream comprises butadiene prior topassing through the hydration unit, and wherein the second processstream comprises less than or equal to 3.0% butadiene by weight prior topassing through the hydration unit.
 12. The method of claim 1, furthercomprising contacting the second process stream with a catalyst withinthe hydration unit, wherein the catalyst comprises at least one ofphosphoric acid, hypophosphorous acid, ion-exchange resin, sulfur,polystyrene, polymer, or niobium oxide.
 13. The method of claim 1,wherein a temperature within the hydration unit is 30° C. to 250° C. anda pressure within the hydration unit is 500 kiloPascals to 20,000kiloPascals.
 14. The method of claim 1, wherein greater than or equal to90% by weight of the butene present in the second process stream isconverted to butanol within the hydration unit.
 15. The method of claim1, further comprising withdrawing a fuel additive product from thehydration unit.
 16. The method of claim 15, wherein the fuel additiveproduct comprises at least one of 2-butanol, tert-butyl alcohol, or C4dimer; wherein the fuel additive product comprises 1 to 50 weight % ofthe at least one of 2-butanol, tert-butyl alcohol, or C4 dimer; andwherein the fuel additive product comprises 1 to 25 weight % oftrimethylpentane.
 17. The method of claim 15, wherein an octane numberof the fuel additive product is greater than 85 in accordance with theAnti-Knock Index.
 18. The method of claim 15, wherein a Reid vaporpressure of the fuel additive product is less than or equal to 15kiloPascals.
 19. The method of claim 1, wherein the recycle streamcomprises butene, and wherein greater than or equal to 90% by weight ofthe butene present in the recycle stream is converted to butane withinthe recycle hydrogenation unit.
 20. A method of producing a fueladditive, comprising: passing a feed stream comprising C4 hydrocarbonsthrough a catalytic cracking unit; passing the feed stream through abutadiene extraction unit producing a first process stream, wherein thebutadiene extraction unit comprises extractive distillation, solventdegassing, solvent regeneration, solvent recovery, or a combinationthereof, and wherein the feed stream comprises butadiene and wherein thefirst process stream withdrawn from the butadiene extraction unitcomprises less than or equal to 5% butadiene by weight; withdrawing abutadiene product from the butadiene extraction unit; passing the firstprocess stream through a methyl tertiary butyl ether unit producing asecond process stream and a methyl tertiary butyl ether product, whereinmethanol and isobutylene are present in the methyl tertiary butyl etherunit in a molar ratio of one mole of isobutylene to 0.1 moles to 5 molesof methanol; withdrawing the methyl tertiary butyl ether product fromthe methyl tertiary butyl ether unit, wherein the first process streamcomprises isobutylene and wherein greater than or equal to 75% by weightof the isobutylene present in the first process stream is converted tomethyl tertiary butyl ether within the methyl tertiary butyl ether unit;passing the second process stream through a hydration unit producing thefuel additive and a recycle stream, wherein a temperature within thehydration unit is 30° C. to 250° C., a pressure within the hydrationunit is 500 kiloPascals to 20,000 kiloPascals, and wherein the secondprocess stream comprises butene and wherein 1.0 to 5090% by weight ofthe butene present in the second process stream is converted to butanolwithin the hydration unit; withdrawing the fuel additive from thehydration unit, wherein the fuel additive comprises at least one of2-butanol, tert-butyl alcohol, or a C4 dimer; passing the recycle streamthrough a recycle hydrogenation unit, wherein the recycle streamcomprises butene and wherein greater than or equal to 90% by weight ofthe butene present in the recycle stream is converted to butane withinthe recycle hydrogenation unit; and recycling the hydrogenated recyclestream from the recycle hydrogenation unit to the catalytic crackingunit.